This disclosure relates to a decorticator, a type of machine designed to separate the outer bast or bark fiber from the inner woody core of plant stalks such as hemp, flax, kenaf, jute, nettles, and other plants in a single operation, using an improved method of rapidly breaking the woody core of bast fiber stalks at very short intervals; rapidly scutching the finely broken core material from the bast fiber; and, accomplishing this action without causing mechanical damage to the bast fiber. This action is equally effective on plant stalks in wet, dry, unretted, or retted condition.
Past and present decortication machines, including but not limited to breakers, scutchers, hammermills, differential speed decorticators, and pre-disintegrators, invariably cause mechanical damage to bast fiber. This mechanical damage is commonly identified as “kink bands.” Typically, the drier the stalk and lesser the degree of retting then the higher the instance of mechanical damage. Most modern decortication systems operate on dry partially retted stalks. The kink bands substantially weaken the bast fiber, thereby limiting the range of end-use applications that it may be used with. For example, when mechanically damaged bast fiber is subjected to wet processing, otherwise referred to as degumming, and additional mechanical processing such as carding, fine cleaning, or cottonization, the mechanically damaged fiber breaks into short fiber under 10 mm in length. Fiber under 10 mm in length has little value and renders attempts to add value through further processing economically unfeasible.
A decorticating machine is described in U.S. Pat. No. 2,460,488, which employs a method of decortication that includes the following components: 1) crushing rolls; 2) feed table; 3) gripping roll; 4) breaking roll; and, 5) scutching roll. The machine operates in the following manner as described below.
First, fibrous plant stalk material is fed longitudinally into two crushing rolls vertically aligned one on top of the other and made of smooth hardened metal. The crushing rolls rotate oppositely and drive the fibrous plant stalks onto a metal feed table which has a gripping roll made of hard rubber positioned above the feed table in close proximity to the feed table edge in order to hold the stalks while continuing to drive the stalks over the edge of the table into the orbit of the breaking roll and then the scutching roll.
Both the breaker and scutcher rolls have a plurality of solid metal blades extending outward longitudinally from the central shaft. The face of the blades is perpendicular to the directional flow of the fibrous materials being acted upon. The two rolls, breaker and scutcher, rotate in opposite directions and their respective blades intermesh in their respective orbital paths to a depth not greater than 1.5 inches.
The forward moving stalks are driven over the feed table edge into the orbital paths of the breaking and scutching rolls. The centers of the breaking and scutching rolls and feed table edge form an approximate 45-45-90 triangle with the ninety degree angle formed between feed table edge and the centers of the breaking and scutch rolls.
The center of the breaking roll is positioned straight out from the feed table edge relatively in line with the plane of the feed table. The orbital path of the breaking roll is down and toward the edge of the feed table. The orbital path clears the edge of the feed table by less than an inch thereby impacting the forward moving stalk bending it down approximately ninety degrees across the feed table edge.
The forward moving stalk continues into the orbital path of the oppositely rotating scutcher roll, which has an orbital path that clears the bottom of the feed table by less than an inch. The blades of the scutcher roll impact the forward moving stalk at substantially the same point of impact as the preceding impact with the breaking roll, but bending the stalk back and up at approximately ninety degrees. The method of decortication involves rapid back and forth bending which breaks, loosens, and allows the bast fiber to be cleaned of woody core without causing serious damage to the fiber. It also allows for operation on plant stalks of varying degrees of moisture content. This method has antecedent in U.S. Pat. No. 1,601,984.
Another decorticating machine is described in U.S. Pat. No. 2,162,780. In this particular decorticator, the breaking and scutching rolls are set at approximately forty five degree angles to the path of the fibrous materials, which are pulled through the breaker and scutcher rolls horizontally at a latitudinal or diagonal angle rather than longitudinally. This prior art also provides for means of arranging sections of blade in a regularly recurrent offset pattern longitudinally across the breaker and scutcher rolls, as well as for means of directing a stream of air from the central shaft of the top breaker roll from the base of the trailing faces of the breaker blades.
The previous prior art examples fail to provide or address the following points of innovation. A means of feeding and compressing a mat of plant stalks into the machine through feed belts position under and above the path of travel. A means of adjusting the angle of the feed table in such a manner that the distance between the point that the stalks clear the feed roller's grip and enter the orbit of the breaker roll can be controlled for optimal performance. A means of controlling the lateral diffusion of plant stalks between the crushing rolls and feed roller with lateral baffle plates. A means of controlling the lateral diffusion of the decorticated fiber through the zone of decortication by providing concave blade tips. A decortication element configuration consisting of a larger upper breaking roll and a smaller lower scutching roll, which results in a unique kinematic action embodied in a faster traveling lower scutcher that sweeps core from fiber. Significantly, this sweeping action may be optimized by altering the pitch point of the lower scutcher in relation to the orbit of the upper breaker resulting in lesser or greater distances between the blades of the scutcher and breaker throughout their orbital intermeshing.